LEROY POFF PROFESSOR OF BIOLOGY COLORADO STATE UNIVERSITY Effect - - PowerPoint PPT Presentation

LEROY POFF

PROFESSOR OF BIOLOGY COLORADO STATE UNIVERSITY

PANELISTS

Effect of NISP on the Poudre River Ecosystem

• N. LeRoy Poff, PhD

Department of Biology Colorado State University

BizWest Water Conference, 18 July 2019

Ecological Health of Poudre River Ecosystem

Physical Biological Chemical

River Health Indicators by Section

River Health Assessment

River is impaired and sensitive to further degradation

How will Glade Reservoir affect Poudre?

City of Fort Collins - ERM

Indicators of River Condition Flow Scenarios Key Reach Scale Drivers (physical, chemical)

Aquatic Insects Algae Channel Structure Rejuvenating Mosaic Riparian Wetlands Native Fish Trout Functioning Riparian Zone

River flow

Poudre River Hydrograph: Key to Sustaining Ecosystem Functions

Floodplain

Fish/insect wetted habitat; Brown trout egg and fry survival Silt flushing

• Insect habitat

Gravel movement

• spawning habitat
• insect habitat

Cobble movement

• bed rejuvenation
• fish/insect habitat

Floodplain inundation

• maintain channel width and heterogeneity
• riparian tree and wetland habitat
• shallow groundwater

Rate of Recession

• cottonwood seedling survival
• groundwater discharge rate

Reduced Average Peaks Dry Streambeds Dry Streambeds

Baseflow

• brown trout spawning and
• verwinter survival

River flow

Projected changes in flows with NISP

Historic and Current Poudre Hydrograph

Full bypass 3 days 2,800 cfs 2 days 1,200 cfs 3 days 2,200 cfs 1 day 1,600 cfs 1 day 0 cfs

Reduced overbanking flows will lead to …

• Direct gradual narrowing
• Thresholds: switch to

upland or dominated by non-natives/pond like system

• Vegetation moving into

the channel, smaller river (with increased flood hazard?)